i just tested this fix over and over again - and it did not work on my server, the file path to the image library is not found.
CI 3.0.6 works. Johns fix for the later version of CI works. Again this is not to say this is universal, it might be something unique in the way the imagemagick library is set up on the server -- I'm just posting this in case other people are having the same issue with imagemagick.